Thursday, July 5, 2018

A Strange Report of "Forensic Epigenetics ... in CODIS"

The “Featured Story” in today’s Forensic Magazine is “Forensic Epigenetics: How Do You Sort Out Age, Smoking in CODIS?” The obvious answer is that you don't and you can't. CODIS records contain no epigenetic data.

What Is Epigenetics?

As a Nature educational webpage explains, “[e]pigenetics involves genetic control by factors other than an individual's DNA sequence. Epigenetic changes can switch genes on or off and determine which proteins are transcribed.” 1/ One chemical mechanism for accomplishing this is DNA methylation, "a chemical process that adds a methyl group to DNA." 2/ More precisely, "methylation of DNA (not to be confused with histone methylation) is a common epigenetic signaling tool that cells use to lock genes in the 'off' position." 3/ This methylation is involved in cell differentiation and hence the formation and maintenance of different tissue types. 4/  "Given the many processes in which methylation plays a part, it is perhaps not surprising that researchers have also linked errors in methylation to a variety of devastating consequences, including several human diseases.” 5/

In forensic genetics, "DNA methylation profiling [has been proposed] for tissue determination, age prediction, and differentiation between monozygotic twins." 6/ Because this "profiling" can uncover health-related and other information as well, discussion of regulating its use by police has begun. 7/

What Is CODIS?

CODIS is “the acronym for the Combined DNA Index System and is the generic term used to describe the FBI’s program of support for criminal justice DNA databases as well as the software used to run these databases.” 8/ The DNA data, which come from twenty locations (loci) on various chromosomes, reveal nothing about methylation patterns. The information from these loci relates solely to the set of underlying DNA sequences. These particular sequences are not transcribed, are essentially identical in all tissues and all identical twins, and do not change as a person ages (except for occasional mutations).

What Is “Sort[ing] Out Age, Smoking in CODIS?”

I don't know. Forensic epigenetics or epigenomics involves neither CODIS databases, CODIS loci, nor CODIS software. Does Forensic Magazine's “Senior Science Writer” think that the databases will be expanded to include epigenetic data? That is not what the article asserts. The only attempt to bridge the two is a concluding sentence that reads, "But some studies, like a Stanford exploration last spring, show that even 13 loci can carry more information than originally believed."

That is not much of a connection, and the statement itself is a trifle misleading. Thirteen is the number of STR loci in CODIS profiles before the expansion to twenty in 2017. The description of the “Stanford exploration” referenced in the article 9/ does not show that the original understanding of the information contained in those core CODIS loci was faulty. Rather, it talks about the growth of the size of the databases and research showing that CODIS profiles “could possibly” be linked to records in medical research databases by “authorized or unauthorized analysts equipped with two datasets, one with SNP genotypes and another CODIS genotypes.” 10/

This possibility does not come as a complete surprise. CODIS profiles are meant to be individual identifiers (or nearly so). If there are genomic databases that sufficiently overlap these regions, then a CODIS profile can be used to locate the record pertaining to the same individual in those databases. The extent to which this possibility is cause for concern is worth considering, 11/ but it has nothing to do with the privacy implications of epigenetic data.

  1. Simmons, D. (2008) Epigenetic influence and disease. Nature Education 1(1):6
  2. Id.
  3. Theresa Phillips (2008) The role of methylation in gene expression. Nature Education 1(1):116.
  4. See, e.g., Karyn L. Sheaffer, Rinho Kim, Reina Aoki, et al. (2014) DNA methylation is required for the control of stem cell differentiation in the small intestine. Genes & Development,; Bo Zhang, Yan Zhou, Nan Lin, et al. (2013) Functional DNA methylation differences between tissues, cell types, and across individuals discovered using the M&M algorithm. Genome Research,
  5. Phillips, supra note 3.
  6. Athina Vidaki & Manfred Kayser (2017) From forensic epigenetics to forensic epigenomics: broadening DNA investigative intelligence, Genome Biol. 18: 238, doi:  10.1186/s13059-017-1373-1
  7. Mahsa Shabani, Pascal Borry, Inge Smeers, & Bram Bekaert (2018) Forensic Epigenetic Age Estimation and Beyond: Ethical and Legal Considerations. Trends in Genet 34(7): 489–491
  8. FBI, Frequently Asked Questions on CODIS and NDIS,
  9. Seth Augenstein, CODIS Has More ID Information than Believed, Scientists Find,” Forensic Mag., May 15, 2017,
  10. Id.
  11. Cf. David H. Kaye, The Genealogy Detectives: A Constitutional Analysis of “Familial Searching,” 51 Am. Crim. L. Rev. 109, 137 n. 170 (2013) (“However, there is at least one rather roundabout way in which the identification profiles could reveal substantial medical information. In the future, when the full genomes of individuals are recorded in clinical databases of medical records, a police agency possessing the profile and having surreptitious access to the database could locate the entry for the individual’s genome and any associated medical records without anyone’s knowledge. Although the STRs would be useful only for identification, that use could be the key to locating information in patient records. Furthermore, the patient’s records and full genome could lead police to the stored genomes and records of relatives. Although I cannot think of many scenarios in which police would be motivated to engage in this computer hacking and medical snooping, there may be some.”).

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